Communication networks are used to transport a variety of signals such as voice, video, data transmission, and the like. Traditional communication networks use copper wires in cables for transporting information and data. However, copper cables have drawbacks because they are large, heavy, and can only transmit a relatively limited amount of data. Consequently, optical waveguide cables replaced most of the copper cables in long-haul communication network links, thereby providing greater bandwidth capacity for long-haul links. However, most communication networks use copper cables for distribution and/or drop links on the subscriber side of the central office. In other words, subscribers have a limited amount of available bandwidth due to the constraints of copper cables in the communication network. Stated another way, the copper cables are a bottleneck that inhibit the subscriber from utilizing the relatively high-bandwidth capacity of the long-haul links.
As optical waveguides are deployed deeper into communication networks, subscribers will have access to increased bandwidth. But there are certain obstacles that make it challenging and/or expensive to route optical waveguides/optical cables deeper into the communication network, i.e., closer to the subscriber. For instance, laying the last mile of fiber to the subscriber requires a low-cost fiber optic cable that is craft-friendly for installation, connectorization, slack storage, and versatility. Moreover, the reliability and robustness of the fiber optic cable must withstand the rigors of an outdoor environment.
FIG. 1 schematically illustrates two different methods for routing fiber optic cables to a premises 19. Specifically, FIG. 1 shows a first method of routing a cable 10 to premises 19 in an aerial application and a second method using a cable 10′ routed to premises 19 in a buried application. In an exemplary aerial application, cable 10 has a first end 10a that is attached at a first interface device 12 located on pole 11 and a second end 10b that is routed to an interface device 14 at premises 19. At the premises the cable is terminated and attached with a clamp such as a P-clamp positioned at a tie point 19a of premises 19. In the aerial application, the fiber optic cable must be able to carry a predetermined tensile load and also withstand wind and ice loading. In buried applications, the first and second ends of cable 10′ are respectively routed to pedestal 18 and connected to interface device 16 and routed and connected to interface device 14. In some buried cable applications, the cable is required to withstand the tensile load associated with pulling the cable through a duct.
Conventional outdoor cables use rigid strength elements having relatively large diameters for carrying tensile loads and inhibiting shrinkage of the cable such as a steel or a glass reinforced plastic rod. However, these relatively large rigid strength members make the cable very stiff and relatively large, but the cable designs preserve optical performance in the outdoor environment. In other words, the conventional outdoor cables were designed to be stiff and inhibit bending, thereby protecting the optical fibers therein. However, these conventional outdoor cables dramatically increased the bending radius of the cable and when coiled the strength members act like a coiled spring that wants to unwind. Consequently, these conventional outdoor cables are difficult for the craft to handle in the field and as well as being difficult to work with in factory because the rigid strength members.
Cables have used other strength members such as conventional fiberglass yarns, but they require a relatively large number of conventional yarns and provide little or no anti-buckling strength compared with rigid strength members. Additionally, these types of cable may not withstand the rigors of the outdoor environment with the desired level of reliability. Moreover, the use of a relatively large number of conventional fiberglass yarns increases the manufacturing complexity along with cost of the cable. Thus, the prior art cables do not meet all of the requirements for a drop cable that is suitable for routing optical waveguides to the subscriber.